Method of making sinuous hard-rubber articles



R. T. GRIFFITHS METHOD OF MAKING' SINUOUS HARD RUBBER ARTICLES April 13 1926.

Filed Dec. 51, 1925 m, m. N

`Paternal Apr. 13, i926.

RICHARD T. GnirfriTHs, oF AKRoN,foHI o, Assiduoit -ToTHn MILLER RUBBER corri PANg'o'F Annen, foHro, A ooRPoRnTioNlonoHio.

METHOD on MAKING sINUoU's- HARD-Riiiaisiiitl ARTICLES.

" [Application flied December 31,1925.. seriai'naxvsu.

To all 'whom t may concern.'

vBe it known that I, RICHARD T. Gnirrrrns, a citizen of the Unitedl States,and resident of Akron, in the countyof Summit and State of Ohio, have invented certain new and use-v ful Improvements in` Methods of Making Y Sinuous Hard-Rubber-Articles, of whichthe following is a specification.

My present invention relatesto'an improved method of making hollow. articles of curved or sinuous form from hardened plastic material, and concerns more particularly a method of producing horns or amplifiers such as used for radio loud speakers and analogous purposes, composed of hard rubber, though not limited to this specific material or use.

Y The makingof articlesof this character has heretofore been rendered YVdiflicultdue to the fact Vthat asl a smooth linterior is necessary, a core must be used to mold such surface, and the removal ofthe core is a problem which has been hard to solve.

, of said layer'.

Thepresent invention aims to provide a method Which will solve the problem and enable the article to be readily and 'economically manufactured no matter how compl-icated its shape.

The invention includes the novel method as hereinafter described, and particularly defined in the appended claims.

In order that the invention may be mor readily understood reference is made to the accompanying drawing, in which Figure l is a sectional View through a horn core and mold, to illustrate the yinitial.

step in the process. 1

Fig. 2 is a view of the horn separated from the mold and core, after the same yhas been bent to the desired shape;

In proceeding according to my invention I apply to the surface of a mandrel or core l, having a straight axis, a layer of rubber compound indicated atA 2, such rubber compound being of a character which when vulcanized will produce `hard rubber. vAround this I-.place a metal reinforcement 3 which is preferably in the shape of a flat wire of metal of such character that it may be bent, and when bent will retain its shape. By the use of a flat Wire or strip as the reinforcement, this may be wound on the layer 2 without being forced'too deeply into-the surface condition as to retain their shape when re- Venclosing layer of plastic material, applying to the surface thereof a reinforcement of bendable metal having spaces through which After the wire has been wound on the surface ofthe layei 2 in spiral form, another layer '4 is applied overlapping the layer 2 with its superposed reinforcement, .and the whole.A is then enclosed in a mold indicatedat 5, which' is subjected to a'temperature 60 sufficient t0. vulcanize the layers 2 and 4; to the consistency of soft rubber, c5: inother '-Words, to semi-Vulcanize them, whereby they are homogeneously united and are in such movedV from the mold and separated from the core, but are capable of being flexed;

After such removahthe'horn or other article is bent to the desired shape such as that shown -in Fig. 2, for example, and the bendable imetal reinforcement causes the hornl to remain inthe shape to which it is bent. Thereafter it may befurther vulcanf ized to-produce the hard rubberl article.-

- Having thus described myinvention, what I claim-is:- y

, 1. The hereind'escribed method of making hollow articles of curved form, from hardened plastic material, which consists in molding they plastic material instraight fo-rm, having incorporated therein a reinforcement of bendable metal, removing the article from the mold and bending it to the desired shape, anll thereafter hardening the plastic materia 2. The hereindescribed method of making hollow articles of curved form from hardened plastic materiaL-which consists in api' plying to a core having a straight axis, an

the plastic -material mayproject, applying thereoverasecond layer of plastic material, Y' y 95 partially hardening the plastic material, removing the vcore, and bending the article to the desired formand thereafter completing the hardening.

3.- The hereindescribed method of making A hollow articles of curved form from hard rubber, which consists in applying a layer of hard vulcanizing rubber compound to a core having a straight axis, winding a strip of bendable metal around said layer, applying a second layer ofqsimilar compo-und thereover, subjecting the rubber compound to a temperature suflicient to partially vulcanize the same, removing the core from the article, bending the article into the desired form, and thereafter subjecting` itrto further vulcanization to complete the cure.

4r. The hereindescrbed method of making hollow articles of curved form from hard rubber, which consists in applying a layer of hard Vulcanizing rubber compound to a core having a straight axis, Winding a strip of flat bendable lnetal around said layer, ap-

10 plying a second layer vof similar compound thereover, subjecting the rubber compound to a temperature suiciernt to partially Vulcanize the same, removing the core from the article, bending the article into the desired forno7 `and thereafter subjecting it to further Vulcanizaton to complete the cure.

In testimony whereof, I ali'ix my signature.

RICHARD T. GRIFFITHS. 

